Detection and diagnosis of disease is usually a necessary prerequisite to treatment and/or curing of the disease. With many inherited diseases, definitive diagnosis must often occur at a molecular level, and typically includes DNA analysis, which can be impractical and expensive owing to the complex and time-consuming procedure inherent to DNA testing. This is especially true of diseases caused by single point mutations, where the historical difficulty in obtaining purified monoclonal antibodies leaves DNA testing as the only viable method of diagnosing disease. While this is true for most diseases caused by single point mutations, one exemplary disease is a clotting disorder associated with a single point mutation of the gene encoding Factor V, known as Factor V Leiden.
To maintain a normal physiological system, it is crucial for blood to travel in an unobstructed manner through the vascular system. When injury occurs to the body, hemostasis assists in clot formation to prevent the loss of blood, while conversely, an anti-coagulant system ensures that the clot is localized at the site of damage, i.e., on the vessel wall, rather than inside blood vessels. Naturally, disturbances in the hemostatic system result in diminished ability to dissolve clots in blood vessels, which can cause traumatic thromboembolitic results. Thromboembolism may cause a variety of dangerous conditions within the body, such as deep vein thrombosis, lung embolism, stroke, and heart attack as normal blood flow from the heart to the body organs is blocked.
The most well-recognized inherited thrombophilic conditions include a resistance to the anti-coagulant Activated Protein C, as well as deficiencies of anti-coagulants, such as Protein C, Protein S, and Antithrombin III deficiencies. For example, Factor V is a blood coagulant that is inhibited by Activated Protein C, which, in turn, prevents blood coagulation. The single point mutation to Factor V, i.e., Factor V Leiden (FVL), causes a resistance to Activated Protein C, thereby preventing the inhibition of blood clotting.
FVL is the most common hereditary blood coagulation disorder in the United States. It is present in 5-8% of the Caucasian population and 1.2% of the African American population. FVL increases the risk of venous thrombosis approximately 3-8 fold for heterozygous and 30-140 folds for homozygous individuals.
Annually, as many as 600,000 hospitalizations and approximately 50,000 deaths are caused by pulmonary embolism alone. It has been estimated that death from pulmonary embolism results within 30 minutes on onset. Despite the widespread belief that FVL is responsible for a significant number of these hospitalizations and fatalities, clinicians do not routinely screen for FVL. This failure to screen may result, in part, from the lack of widely accepted detection methods.
Presently, most accurate FVL detection methods require DNA analysis, which are impractical for routine screening, as they are very expensive and time-consuming, and they do not provide a level for FVL in plasma. Consequently, FVL is usually screened with a clotting assay that is not sufficiently specific for FVL. Further, it can be difficult for a clotting assay to distinguish between FVL and other types of blood clotting disorders, such as deficiencies in Protein C or Antithrombin III. In fact, because FVL results in a resistance to Activated Protein C, FVL and Protein C deficiency may be indistinguishable with current assay protocols.
In view of the large population of affected individuals, early screening of FVL could make affected individuals aware of their high risk for thromboembolic complications and encourage them to take preventive actions. This may help to avoid the enormous after-care expenses incurred by victims—including physical debilitation and also emotional stress.